A contact lens under development is of a type that is mounted, for example, during sleep and changes the corneal shape of a patient, thereby correcting myopia, hyperopia, and/or astigmatism while the contact lens is removed.
When the above-described contact lens is not mounted for a long period of time, the restoring force of the cornea restores the original myopia or hyperopia state. It is thus desirable to fix the cornea in a corrected state.
On the other hand, in a refraction correction surgery, while riboflavin (vitamin B2) is infiltrated, a corneal tissue is irradiated with UV rays for crosslinking collagens constituting the cornea, thereby enhancing the corneal strength and fixing the cornea.
For corneal crosslinking, a retractor is used to keep open the eye of a patient, and a riboflavin solution is dropped from a cylindrical reservoir part mounted above the cornea so as to be infiltrated into the cornea.
Also, in Patent Literature 1, the present inventor proposed a contact lens for corrective corneal crosslinking and a crosslinking method for cornea correction.
In this method, a crosslinking method and a contact lens of cornea correction are combined to fix the corneal shape in a state where the cornea is corrected by the contact lens to a certain extent.
Also in this case, infiltration of a riboflavin solution is performed in a state where the contact lens for cornea correction is removed as in the case of the above-mentioned method.
The foregoing methods have the following problems: to drop and infiltrate a riboflavin solution with the eye of a patient open, the patient is restrained by a retractor under the state of having to keep the eye opened for a long period of time (about 30 minutes); and since the dropped riboflavin solution does not completely infiltrate into the cornea and most of the solution leaks outside, a physician needs to frequently perform the task of blotting up the leaked riboflavin solution. Furthermore, when UV irradiation is performed, a contact lens is mounted after a riboflavin solution infiltrates into the cornea. The problem is that the deformation characteristics of the cornea differ from those before infiltration of the riboflavin solution, making it impossible to sufficiently correct the cornea.
As in the case of the conventional contact lens, the aforementioned contact lens for cornea correction is produced on the basis of the design concept that the thickness should be as small as possible (currently, the lens thickness at the central part is 0.14 mm or greater and 0.25 mm or smaller). Thus, the problem of the aforementioned contact lens for cornea correction is that the contact lens is likely to crack.
This contact lens for cornea correction is formed by grinding and cutting out from a circular-plate material, which is usually called a button, with a diameter of 10 mm and a height of 5 mm. In the production process thereof, one surface is first ground and cut out, and the other surface is ground while the ground and cut out surface to which a curved shape is given is supported, to form the contact lens, for example, disclosed in Patent Literature 1. The problem of this production process is that the lens material is eventually broken when the other surface is ground.